3 yo has resurrected daytime naps AND early waking - help!

[milkmoustache]

DD has recently started waking around 6am, but for ages she was going until 7am or so - I know, lucky us! BUT she has also started to put herself to bed for a daytime nap at midday, often just before lunch, which can last for 2 hrs plus. For a couple of months she went without any day sleep at all and seemed fine, but I am confused by this development esp. since she hasn't even started pre-school and we aren't doing anything new or particulaly tiring at the minute. DH is convinced that we need to stop the daytime sleep in order to get a more reasonable start in the morning - any thoughts?